Table 1 Characteristics of the included studies

Proestakis, 2018 [29] Italy

Study design: Cluster RCT.

Sample characteristics: 349 children (9–11 years old), 177 females and 172 males, from 19 fifth-grade elementary school classes in the same region. IG “Individual regards” (n = 87); IG “Direct reciprocity” (n = 50; IG “Indirect reciprocity” (n = 61); IG “Team rewards” (n = 75); CG (n = 76).

PA and SB measurements: Accelerometry. SB: No measured.

Supporting theory: Social network theory.

Social function promoted: Social norms, social influence, and social pressure.

Intervention: 7-week intervention to different social incentives in two experimental phases. Five conditions groups were established—four groups in intervention. Students were matched with classmates of the same sex and strong ties (best friends). Three intervention conditions of social-rewards schemes were established: Direct reciprocity, indirect reciprocity, and team rewards, in which classmates’ rewards depend on the PA of two friends either reciprocally (directly or indirectly) or collectively. Additionally, one intervention condition of individual rewards was established. The control group was established with a random reward.

SNI approach: Induction and alteration.

Effects: Compared with a random-rewards control, social-rewards schemes have an overall significantly positive effect on PA.

Bell, 2017 [32] England

Study design: Exploratory RCT.

Sample characteristics: 928 adolescents (12–13 years old) from six co-educational comprehensive schools. IG (n = 462); CG: n = 466).

PA and SB measurements: Accelerometry.

Supporting theory: DOI.

Social function promoted: Social influence and social support.

Intervention: 10-week intervention, informed by a focus group with students, interviews with professional persons, and document review. Peer supporters were identified by nominations and then trained to play a supporter role within their classrooms to encourage peers in PA and decrease sedentary time. The control group received no intervention.

SNI approach: Individual.

Effects: No effects on PA or SB

Woudenberg, 2018 [28] Netherlands

Study design: Cluster RCT.

Sample characteristics: 190 adolescents (11–14 years old) from a school. IG: Five classrooms (n = 93); CG: six classrooms (n = 97).

PA and SB measurements: PA: Accelerometry. SB: No measured.

Supporting theory: SDT and self-persuasion theory.

Social function promoted: Social influence and social modeling.

Intervention: 1-week intervention. Influence agents (team captains) were nominated by peers and trained via smartphones to implement the intervention, with daily follow-up. The influence agents were trained to promote PA in the classroom through four strategies: Social facilitation, modeling, example and acting, and impression management. The control group received no intervention.

SNI approach: Individual.

Effects: No effects on PA

Woudenberg, 2020 [27] Netherlands

Study design: Clustered RCT.

Sample characteristics: 446 children and adolescents (9–16 years old) from 11 schools. (IG “social network”: 7 classes n = 131; IG “mass media”: 7 class n = 123; CG: 12 class n = 192).

PA and SB measurements: PA: Accelerometry. SB: No measured.

Supporting theory: Theory of planned behavior and SDT.

Social function promoted: Social influence and social norms.

Intervention: 1-week intervention. Influence agents were nominated by peers and trained to implement the intervention, creating PA vlogs based on peers’ different social influence components. They did not receive training in how they can influence the PA of peers. In the mass media intervention, participants were exposed to vlogs made by unfamiliar peers. The control group received no intervention.

SNI approach: Individual.

Effects: No effects on PA

Jago, 2021 [33] England

Study design: Cluster RCT.

Sample characteristics: 1558 girls (13–14 years old) from 20 state-funded secondary schools from three broad regions. IG: 10 schools (n = 758); CG: 10 schools (n = 800).

PA and SB measurements: Accelerometry

Supporting theory: DOI and SDT.

Social function promoted: Social support.

Intervention: 10-week intervention based on the ASSIST intervention model. Peer supporters were identified by nominations and then trained for three days to play a supporter role within their classrooms to promote PA among their peer group. The training covered PA importance, how to be active, initiate conversations with peers about PA, and encourage peers to be active. The CG received no intervention.

SNI approach: Individual.

Effects: No effects on PA or SB

Sebire, 2018 [34] England

Study design: Feasibility RCT.

Sample characteristics: 427 girls (12–13 years old) from six state more deprived secondary schools. Fifty-three were trained as peer supporters. IG = 4 schools (n = 269); CG: 2 schools (n = 158)

PA and SB measurements: Accelerometry

Supporting theory: DOI and SDT.

Social function promoted: Social influence.

Intervention: 10-week intervention based on the ASSIST intervention model. Briefly, it comprised (a) peer-supporter nomination, (b) a train-the-trainers program, and (c) peer-supporter training followed by a 10-week informal PA message diffusion period. Control schools did not receive the intervention.

SNI approach: Individual.

Effects: Intervention had the potential to positively affect adolescent girls’ MVPA and reduce ST compared to controls 4–5 months post-intervention.

Barr-Anderson, 2012 [35] USA

Study design: Quasi-experimental feasibility study.

Sample characteristics: 148 6th-grade students (age mean 11.2) from 4 schools in metropolitan areas with racially/ethnically diverse students. IG: 2 schools (n = 87); CG: 2 schools (n = 61).

PA and SB measurements: PA: Previous Day Physical Activity Recall (PDPAR). SB: not measured.

Supporting theory: SCT.

Social function promoted: Social influence, social support, and social norms.

Intervention: 6-week intervention. The two intervention schools received the enhanced PALA + Peers program. The intervention included DVD of PA made by peers to encourage PA, training peer-led (n = 28) nominated to lead classroom sessions with teachers, PA, and healthy eating. Control schools received the standard PALA program.

SNI approach: Individual.

Effects: The intervention was successful in increasing moderate PA in all students and MVPA in girls